Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Thu, 26 Sep 2019 16:38:35 +0200
From:   Marco Felsch <m.felsch@pengutronix.de>
To:     Adam Thomson <Adam.Thomson.Opensource@diasemi.com>
Cc:     "broonie@kernel.org" <broonie@kernel.org>,
        Support Opensource <Support.Opensource@diasemi.com>,
        "lee.jones@linaro.org" <lee.jones@linaro.org>,
        "robh+dt@kernel.org" <robh+dt@kernel.org>,
        "lgirdwood@gmail.com" <lgirdwood@gmail.com>,
        Steve Twiss <stwiss.opensource@diasemi.com>,
        "kernel@pengutronix.de" <kernel@pengutronix.de>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/5] dt-bindings: mfd: da9062: add regulator voltage
 selection documentation
Message-ID: <20190926143835.tjv535h4gnfyystk@pengutronix.de>
References: <20190917124246.11732-1-m.felsch@pengutronix.de>
 <20190917124246.11732-3-m.felsch@pengutronix.de>
 <AM5PR1001MB0994ABEF9C32BFB7BEA099B680840@AM5PR1001MB0994.EURPRD10.PROD.OUTLOOK.COM>
 <20190925155151.75uaxfiiei3i23tz@pengutronix.de>
 <AM5PR1001MB09941810C3AE97110DD82E0F80870@AM5PR1001MB0994.EURPRD10.PROD.OUTLOOK.COM>
 <20190926080956.a3k2z4gf3n6m3n4s@pengutronix.de>
 <AM5PR1001MB09944C0F9A4F547BF9E175CF80860@AM5PR1001MB0994.EURPRD10.PROD.OUTLOOK.COM>
 <20190926114354.qvv2rs7mc4xh6lkp@pengutronix.de>
 <AM5PR1001MB099405D4A0C06CD6BF2886E880860@AM5PR1001MB0994.EURPRD10.PROD.OUTLOOK.COM>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <AM5PR1001MB099405D4A0C06CD6BF2886E880860@AM5PR1001MB0994.EURPRD10.PROD.OUTLOOK.COM>
User-Agent: NeoMutt/20170113 (1.7.2)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 19-09-26 14:04, Adam Thomson wrote:
> On 26 September 2019 12:44, Marco Felsch wrote:
> 
> > On 19-09-26 10:17, Adam Thomson wrote:
> > > On 26 September 2019 09:10, Marco Felsch wrote:
> > >
> > > > On 19-09-25 16:18, Adam Thomson wrote:
> > > > > On 25 September 2019 16:52, Marco Felsch wrote:
> > > > >
> > > > > > Hi Adam,
> > > > > >
> > > > > > On 19-09-24 09:23, Adam Thomson wrote:
> > > > > > > On 17 September 2019 13:43, Marco Felsch wrote:
> > > > > > >
> > > > > > > > Add the documentation which describe the voltage selection gpio
> > > > support.
> > > > > > > > This property can be applied to each subnode within the 'regulators'
> > > > > > > > node so each regulator can be configured differently.
> > > > > > > >
> > > > > > > > Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
> > > > > > > > ---
> > > > > > > >  Documentation/devicetree/bindings/mfd/da9062.txt | 9 +++++++++
> > > > > > > >  1 file changed, 9 insertions(+)
> > > > > > > >
> > > > > > > > diff --git a/Documentation/devicetree/bindings/mfd/da9062.txt
> > > > > > > > b/Documentation/devicetree/bindings/mfd/da9062.txt
> > > > > > > > index edca653a5777..9d9820d8177d 100644
> > > > > > > > --- a/Documentation/devicetree/bindings/mfd/da9062.txt
> > > > > > > > +++ b/Documentation/devicetree/bindings/mfd/da9062.txt
> > > > > > > > @@ -66,6 +66,15 @@ Sub-nodes:
> > > > > > > >    details of individual regulator device can be found in:
> > > > > > > >    Documentation/devicetree/bindings/regulator/regulator.txt
> > > > > > > >
> > > > > > > > +  Optional regulator device-specific properties:
> > > > > > > > +  - dlg,vsel-sense-gpios : The GPIO reference which should be used
> > by
> > > > the
> > > > > > > > +    regulator to switch the voltage between active/suspend voltage
> > > > settings.
> > > > > > If
> > > > > > > > +    the signal is active the active-settings are applied else the suspend
> > > > > > > > +    settings are applied. Attention: Sharing the same gpio for other
> > > > purposes
> > > > > > > > +    or across multiple regulators is possible but the gpio settings must
> > be
> > > > the
> > > > > > > > +    same. Also the gpio phandle must refer to to the dlg,da9062-gpio
> > > > device
> > > > > > > > +    other gpios are not allowed and make no sense.
> > > > > > > > +
> > > > > > >
> > > > > > > Should we not use the binding names that are defined in 'gpio-
> > > > regulator.yaml'
> > > > > > as
> > > > > > > these seem to be generic and would probably serve the purpose here?
> > > > > >
> > > > > > Hm.. as the description says:
> > > > > >
> > > > > > 8<--------------------------------------------------
> > > > > > gpios:
> > > > > >    description: Array of one or more GPIO pins used to select the
> > > > > >    regulator voltage/current listed in "states".
> > > > > > 8<--------------------------------------------------
> > > > > >
> > > > > > But we don't have a "states" property and we can't select between
> > > > > > voltage or current.
> > > > >
> > > > > Yes I think I was at cross purposes when I made this remark. The bindings
> > there
> > > > > describe the GPOs that are used to enable/disable and set voltage/current
> > for
> > > > > regulators and the supported voltage/current levels that can be configured
> > in
> > > > > this manner. What you're describing is the GPI for DA9061/2. If you look at
> > > > > GPIO handling in existing regulator drivers I believe they all deal with
> > external
> > > > > GPOs that are configured to enable/disable and set voltage/current limits
> > > > rather
> > > > > than the GPI on the PMIC itself. That's why I'm thinking that the
> > configurations
> > > > > you're doing here should actually be in a pinctrl or GPIO driver.
> > > >
> > > > That's true, the common gpio bindings are from the view of the
> > > > processor, e.g. which gpio must the processor drive to enable/switch the
> > > > regualtor. So one reasone more to use a non-common binding.
> > > >
> > > > Please take a look on my other comment I made :) I don't use the
> > > > gpio-alternative function. I use it as an input.
> > >
> > > I know in the datasheet this isn't marked as an alternate function specifically
> > > but to me having regulator control by the chip's own GPI is an alternative
> > > function for that GPIO pin, in the same way a specific pin can be used for
> > > SYS_EN or Watchdog control. It's a dedicated purpose rather than being a
> > normal
> > > GPI.
> > 
> > Nope, SYS_EN or Watchdog is a special/alternate function and not a
> > normal input.
> 
> Having spoken with our HW team there's essentially no real difference.

So I don't have to configure the gpio to alternate to use it as SYS_EN?

> > 
> > > See the following as an example of what I'm suggesting:
> > >
> > >
> > https://elixir.bootlin.com/linux/latest/source/Documentation/devicetree/bindin
> > gs/pinctrl/pinctrl-palmas.txt
> > >
> > > You could then pass the pinctrl information to the regulator driver and use
> > > that rather than having device specific bindings for this. That's at least my
> > > current interpretation of this anyway.
> > 
> > For me pinctrl decides which function should be assigned to a pin. So in
> > our case this would be:
> >   - alternate
> >   - gpo
> >   - gpi
> > 
> > In our use-case it is a gpi..
> 
> It's not being used as a normal GPI as such. It's being used to enable/disable
> the regulator so I disagree.

This one is used as voltage-selection. What is a "normal" GPI in your
point of view?

> > 
> > An other reason why pinctrl seems not be the right solution is that the
> > regulator must be configured to use this gpi. This decision can't be
> > made globally because each regulator can be configured differently.. For
> > me its just a local gpio.
> 
> You'd pass pinctrl information, via DT, to the regulator driver so it can set
> accordingly. At least that's my take here, unless I'm missing something. The
> regulator driver would be the consumer and could set the regulator control
> accordingly.

IMHO this is what I have done. I use the gpi so the regulator is the
consumer. Since the gpi can be used by several regulators for voltage
selection or enable/disable action this gpi is marked as shared. If I
got you right than you would do something like for regulatorX.

  pinctrl-node {

  	gpio2 {
		func = "vsel";
	}
  }

But the gpi(o)2 can also be used to enable/disable a regulatorY if I
understood the datasheet correctly. I other words:


         +--> Alternate function
      /
  ---+   +--> GPI ----> Edge detection ---> more processing
   |       |                |
   |       |                +-----> Regulator control
   |       |                          |
   \__  __/ \__________  _______
      \/               \/
   pinctrl            gpio

This is how I understood the pinctrl use-case. I configure the pin as
gpio and then the regulator driver consume a gpio.

> At the end of the day I'm not the gatekeeper here so I think Mark's input is
> necessary as he will likely have a view on how this should be done. I appreciate
> the work you've done here but I want to be sure we have a generic solution
> as this would also apply to DA9063 and possibly other devices too.

Why should this only apply to da9062 devices? IMHO this property can be
used by any other dlg pmic as well if it is supported. Comments and suggestions
are welcome so no worries ;)

Regards,
  Marco

> Have added Mark to the 'To' in this e-mail thread so he might see it.
> > 
> > Regards,
> >   Marco
> > 
> > > >
> > > > Regards,
> > > >   Marco
> > > >
> > > >
> > > > > I'd be interested in hearing Mark's view on this though as he has far more
> > > > > experience in this area than I do.
> > > > >
> > > > > >
> > > > > > Regards,
> > > > > >   Marco
> > > > > >
> > > > > > > >  - rtc : This node defines settings required for the Real-Time Clock
> > > > associated
> > > > > > > >    with the DA9062. There are currently no entries in this binding,
> > however
> > > > > > > >    compatible = "dlg,da9062-rtc" should be added if a node is created.
> > > > > > > > --
> > > > > > > > 2.20.1
> > > > > > >
> > > > > > >
> > > > > >
> > > > > > --
> > > > > > Pengutronix e.K.                           |                             |
> > > > > > Industrial Linux Solutions                 | http://www.pengutronix.de/  |
> > > > > > Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0
> > |
> > > > > > Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |
> > > > >
> > > >
> > > > --
> > > > Pengutronix e.K.                           |                             |
> > > > Industrial Linux Solutions                 | http://www.pengutronix.de/  |
> > > > Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    |
> > > > Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |
> > >
> > 
> > --
> > Pengutronix e.K.                           |                             |
> > Industrial Linux Solutions                 | http://www.pengutronix.de/  |
> > Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    |
> > Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |
> 

-- 
Pengutronix e.K.                           |                             |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |